Scott Walker’s presidential campaign has hit a rough patch, as we’ve already noted. He’s trying to right the wheelbarrow and get things back on the garden path – and maybe draw some media attention away from Donald Trump – so on Tuesday, the Wisconsin governor released a big proposal to repeal and replace Obamacare.

Is this a smart move? In political terms, it could well be. GOP voters generally detest Obamacare, so Governor Walker might be able to use the subject of health care to sidestep continued questions about immigration and other Trump-driven agenda items. He can point to the “replace” part of the proposal as evidence that he’s got serious plans for action on Oval Office Day 1.

Furthermore, it provides him an opportunity to take a slap at the current GOP electoral leadership. The party controls the House and Senate, right? Why haven’t they put a bill to repeal Obamacare on President Obama’s desk?

“A Republican Party that wants to govern should actually know what it wants to do with the health care system in America,” writes Pascal-Emmanuel Gobry in The Week magazine. “And critically, it’s no longer smart politics to be hush-hush about it: Any Republican president is going to have to sell the American people on a genuine vision of where to take the health care system.”

But from a policy point of view, the implications of Walker’s plan may be a bit different. If nothing else, they show a tough truth about the American health-care system: It’s so complicated that it’s really hard to design a viable plan for sweeping change.

Walker would get rid of Obamacare’s system of state-based health insurance exchange marketplaces and income-based tax credit subsidies. In its place, he’d erect a system where taxpayers get an age-based tax-credit subsidy to help them buy private health plans.

Not that different? Well, Walker would eliminate O’care’s requirement that Americans have health insurance, so that would be one major change.

But Walker’s subsidies top out at $3,000 a person for over-50-year-olds. For 18-to-34s, the tax-credit subsidy would be $1,200 per year. Is that enough to buy good health coverage in most of the US? That’s an open question.

That leaves Walker open to a Democratic charge that he’s going to lower the percentage of Americans with insurance plans.

On the other hand, Walker’s plan wouldn’t be cheap. He would deal with preexisting conditions by broader use of state high-risk pools, which in practice have proved to be extremely expensive. Plus, he’d eliminate all Obamacare’s sources of revenue, without really specifying what would replace them.

In the opinion of health-care expert Avik Roy, an adviser to 2016 rival Gov. Rick Perry, Walker’s proposal would cost about $1.1 trillion over 10 years. Yet it devotes only two sentences to outlining how this might be paid for.

“The point is, it’s easy to promise to expand coverage or replace Obamacare. What’s hard is paying for it in ways that are politically viable,” writes Mr. Roy in Forbes.

This leaves Walker open to criticism from the right that he's proposing to repeal Obamacare and replace it with Obamacare-light. Call it Walkercare.

“Governor Walker makes the same mistake President Obama did: creating a new entitlement program we can’t afford,” tweeted Louisiana Gov. Bobby Jindal, another GOP presidential hopeful, on Tuesday.

The design, passage, and implementation of Obamacare was a massive policy struggle that consumed Washington for a lengthy period. For better or worse, it’s one of the defining legacies of Mr. Obama’s presidency. What Walker’s plan might reveal is that replacing Obamacare, at this point, might require a similar effort on the part of any Republican chief executive.